From: George Rasko ([email protected])
Date: Thu Dec 07 2000 - 17:21:13 PST
-----Original Message-----
From: George Rasko
Sent: Thursday, December 07, 2000 9:40 AM
To: '[email protected]'
Subject: RE: [SI-LIST] : One Differential To Another
Richard,
I got a few comments back, generally along the lines of what you said:
- differentail impedance is differential impedance = there won't be
reflections
if the impedances are same, no matter how that is achieved.
- that being said, common mode signals and noise will be reflected and not
attenuated
if the common mode impedances are not the same.
- making a differential pair by putting opposite polarity signals on
opposite sides of
a plane probably gives little common mode rejection, since the
electromagnetic
environments on the opposite sides of the plane are likely
different.
Thanks for asking,
George
-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: Thursday, December 07, 2000 5:40 AM
To: George Rasko; [email protected]
Subject: Re: [SI-LIST] : One Differential To Another
George, I was wondering if you ever got an answer to your question on the SI
list.
In my opinion, the differential signal fidelity shouldn't be affected by
changing from a coupled pair to an uncoupled pair as long as the
differential
impedance stays constant. The coupled line would be less susceptible to
crosstalk from an aggressor trace, however. A tighter coupled pair would
have better performance in the presence of crosstalk (higher common mode to
differential mode crosstalk ratio) than a lightly coupled pair.
Richard Ellison
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